(1) Field of the Invention
The present invention is the field of equipment for an aircraft fitted with at least one rotor, an airplane having a propulsive propeller, or more specifically a rotorcraft. The present invention relates more particularly to electrical connector devices for electrical connection between a hub and the blades of a rotor of the aircraft. Such an electrical connector provides electrical power to apparatus that is incorporated in each of the blades individually, in particular de-icer apparatus for de-icing such a blade by electric heating.
(2) Description of Related Art
Aircraft include aircraft that are provided with at least one rotor having a plurality of blades. The blades are mounted radially distributed on a hub for driving them in rotation, the hub itself being driven in rotation by a drive source of the aircraft. In particular, such a drive source is formed of a main gearbox that is driven by a power plant of the aircraft.
By way of example, for an airplane having lift that is obtained by a fixed wing, at least one rotor formed of a propulsive propeller propels the airplane in translation.
Also by way of example, for a rotorcraft, at least one rotary wing is formed of a main rotor having a substantially vertical axis, which main rotor provides the rotorcraft at least with lift, and possibly also propels it in translation and/or guides it in flight. Rotorcraft are also commonly provided with an auxiliary rotor such as a tail rotor or a propulsive propeller in the context of a rotorcraft that is fast and that has a long range. Such an auxiliary rotor is commonly used to guide the rotorcraft in yaw, or even to propel it in translation for a rotor formed of a propulsive propeller for propelling the rotorcraft in translation.
In order to vary the thrust exerted by a propulsive propeller or a said tail rotor, or in order to vary the lift provided by a said main rotor, rotor aircraft are provided with means for varying the collective pitch of the blades of at least one of their rotors. Varying the collective pitch of the blades makes it possible to increase the thrust exerted by the rotor, such as in lift for a said main rotor, such as in yaw for a said tail rotor, or such as in propulsion in translation for a said propulsive propeller.
Specifically for a helicopter, the main rotor not only provides the rotorcraft with lift, but also propels it and/or guides it in flight. Varying the pitch of the blades of the main rotor is not only a variation of the collective pitch so as to modify the lift and the propulsion of the rotorcraft, but it is also a variation of the cyclic pitch so as to modify the behavior of the rotorcraft in flight, both in pitching and in roll.
In order to make it possible to vary their pitch collectively and/or where appropriate cyclically, the blades are mounted on the hub to pivot individually in their general plane, by means of respective blade roots. In various variant embodiments, a blade root may be incorporated in the blade for mounting the blade on the hub, or it may be formed of a junction member that carries a blade and that is mounted on the hub. By way of indication, the blades pivot on the hub through an angular extent of plus or minus 120°.
The blades are suitable for incorporating, or for being fitted individually with, one or more kinds of electrical apparatus, such as a de-icer apparatus in particular. This poses the problem of installing means on the rotor, means for delivering electrical power from the hub to the blades despite them being pivotally mounted on the hub.
The hub is provided with an electrical power take-off making it possible to power said electrical apparatus fitted individually on the blades. Such a take-off is fed with electrical power from an electrical power source that is fitted on the aircraft, such as an on-board electricity network or any other electrical power resource of the aircraft. The hub is provided with electrical connection means for connecting to said on-board network via a mast that carries the hub. By way of example, such connector means are rotary means having slip rings or other similar means for electrically connecting two members that rotate relative to each another.
Each blade is electrically connected to said take-off via a flexible wired connection for connecting a connector on the hub with a connector on the blade. The wired connection may be made up of one or more wires depending on the electricity needs of the blade. Traditionally, the connection between the blade and the electricity take-off is maintained, despite the pivoting of the blades on the hub, by taking advantage of the flexibility and of the appropriate length of the wired connection.
However, the blades are placed on the rotorcraft in an environment that is hostile and they are subjected to large centrifugal forces. The wired connections need to withstand such hostile environments and centrifugal forces, in addition to the twisting stresses to which they are subjected under the effect of the blades pivoting. Consequently, the structure of the wired connections needs to be robust, whilst nevertheless being compatible with the need for being flexible. However, frequent maintenance operations are necessary. Such maintenance operations are costly, both in terms of the intrinsic cost of the wired connections, and in terms of the operations required to replace them.
Moreover, in addition to their individual de-icers, the blades are also potentially fitted with various other kinds of electrical apparatus. By way of example, it is known to incorporate a device in the blades that makes it possible to vary the angle of incidence of the blades by twisting them in their general plane. Such devices commonly use at least one electrical apparatus that needs to be powered with electricity. Complicating the blades in this way results in an increase in the number of wires that must be incorporated in the wired connections, to the detriment of their flexibility, or in an increase in the number of said wired connections for each of the blades.
In this context, various solutions have been proposed to mitigate the drawbacks induced by the frequent maintenance operations on such wired connections.
By way of example, it has been proposed to simplify the ways in which wired connections can be connected to the hub and to the blades respectively, so as to make maintenance operations easier to perform.
By way of example, it has also been proposed to protect the wired connections from the hostile environment of the rotor, by protecting them with caps. However, such a protection solution presents the drawback of affecting the ability of the wired connections to move over themselves, thus presenting difficulty for the wired connections to accompany the pivoting movements of the blades, or to adapt in shape under the effect of the centrifugal forces that are generated by the rotor rotating.
In order to understand the difficulties to be overcome, and in order to discover the technological background close to the context of the present invention, reference can be made to documents U.S. Pat. No. 5,174,717 (SAFEWAY PRODUCTS INC) and U.S. Pat. No. 6,358,006 (THE BF GOODRICH COMPANY), or to document U.S. Pat. No. 5,709,532 (THE BF GOODRICH COMPANY) and document FR 2 793 469 (WL GORE ASS. INC.).
It has also been proposed by document U.S. Pat. No. 3,042,346 (HAWLEY JAMES F) to equip a propulsive propeller with flanges that guide an elastically-deformable wiring harness between them, which harness electrically connects a pivotable blade to a rotary hub of the propulsive propeller. The harness is contained in a gap that protects it from the centrifugal forces that are generated under the effect of the rotor rotating, the ability of the harness to deform elastically making it possible to vary its length between the blade and the hub so as to accompany the pivoting of the blade on the hub.